Adult educators are becoming increasingly aware of the fact that adult learners, not institutions, initiate the process of adult education and that they determine the ends to be accomplished by their participation. Researchers have shown that the decision to participate in adult education comes about as a result of a variety of social and environmental factors. Perhaps McClusky's Theory of Margin can give a fresh perspective when it is applied to a model of participation in adult education. Margin, which is the difference between an individual's aggregate load (obligations) and power (social, mental, physical, economic, and life skills), is a factor that can make the difference between choosing to participate in a learning endeavor or not. A diagnostic instrument designed to measure an individual's margin could serve as a valuable tool that would enable educational brokers to assist adult learners in defining goals, setting objectives, and gaining access to learning resources. The Theory of Margin is applicable in an identification of an individual's potential participation in adult education inasmuch as the following participation factors are components of either load or power: socioeconomic status, learning press, attitude toward the value of adult education, readiness to participate in adult education, and participation stimuli. Thus, cooperative diagnostic tools for measuring margin could contribute greatly to the educational brokering process. (MN)